JP7119598B2 - Contactless power transmission device and contactless power transmission system - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a contactless power transmission device and a contactless power transmission system, and more particularly to control technology for an inverter in a contactless power transmission device that wirelessly transmits power to a power receiving device.

2. Description of the Related Art A power transmission system that transmits power from a power transmission device to a power reception device in a contactless manner is known (see Patent Documents 1 to 5, for example). In such a power transmission system, the power transmission device includes an inverter that generates transmission power of a predetermined frequency and supplies it to the power transmission section. In an inverter, if an output current (turn-on current) with the same sign as the output voltage flows when the output voltage rises due to switching operation, a reverse short-circuit current (recovery current) flows through the free wheel diode during switching operation. . As a result, the freewheeling diode and the switching element, through which the short-circuit current flows, generate a large amount of heat, which increases the loss and may lead to abnormal overheating. The fact that the turn-on current flows when the inverter output voltage rises corresponds to the fact that the phase of the output current is advanced with respect to the output voltage.

Japanese Patent Application Laid-Open No. 2016-111902 (Patent Document 6) discloses a technique for suppressing the recovery current. In the power transmission device described in Patent Literature 6, when the phase of the output current of the inverter is advanced with respect to the output voltage, the frequency of the power to be transmitted is manipulated so that the advance of the current phase becomes smaller. Specifically, a map showing the relationship between the coupling coefficient between the power transmitting unit and the power receiving unit, the frequency of the transmitted power, and the current phase with respect to the voltage phase is prepared in advance, and the calculated value of the coupling coefficient and the map are prepared. is used to adjust the frequency in the direction in which the advance angle of the current phase decreases (that is, in the direction in which the turn-on current decreases). As a result, the turn-on current is suppressed, and the recovery current can be suppressed (see Patent Document 6).

JP 2013-154815 A JP 2013-146154 A JP 2013-146148 A JP 2013-110822 A JP 2013-126327 A JP 2016-111902 A

The power transmission device described in Patent Literature 6 requires a map showing the relationship between the coupling coefficient, the frequency, and the current phase with respect to the voltage phase to be prepared in advance by experiments or the like, and the generation of the map requires many man-hours and costs. there is a possibility. Furthermore, the relationship between the frequency and the above phase (i.e., the relationship between the frequency and the turn-on current) may be affected by temperature, etc., and there is a possibility that the map, etc., may make a mistake in the operation direction of the frequency that reduces the turn-on current. be.

The present disclosure has been made to solve such a problem. It is to suppress.

A contactless power transmission device according to the present disclosure includes a power transmission unit, an inverter, and a control unit. The power transmission unit is configured to wirelessly transmit power to the power receiving device. The inverter generates transmission power of a predetermined frequency and supplies it to the power transmission section. The control unit is configured to perform turn-on current control for controlling the turn-on current to be equal to or less than a limit value by manipulating the frequency of transmitted power using the inverter. The turn-on current control includes a first process of determining the direction of frequency operation for decreasing the turn-on current based on the direction of change in the turn-on current when the frequency is changed.

A contactless power transmission system according to the present disclosure includes a power transmitting device and a power receiving device that wirelessly receives power from the power transmitting device. The power transmission device includes a power transmission section, an inverter, and a control section. The power transmission unit is configured to wirelessly transmit power to the power receiving device. The inverter generates transmission power of a predetermined frequency and supplies it to the power transmission section. The control unit is configured to perform turn-on current control for controlling the turn-on current to be equal to or less than a limit value by manipulating the frequency of transmitted power using the inverter. The turn-on current control includes a first process of determining the direction of frequency operation for decreasing the turn-on current based on the direction of change in the turn-on current when the frequency is changed.

According to the contactless power transmission device and the contactless power transmission system described above, the direction of frequency operation for decreasing the turn-on current is determined based on the direction of change in the turn-on current when the frequency of the transmitted power is actually changed. Therefore, the turn-on current can be reliably suppressed.

The control unit may be configured to further perform power control for controlling transmission power with a target and efficiency optimum control. Efficiency optimum control is control that seeks the optimum frequency for improving efficiency by oscillating the frequency under the condition that transmission power is controlled to a target by power control. The first process may include a process of determining the direction of frequency operation based on the direction of change in the turn-on current according to the frequency oscillation in the optimum efficiency control.

According to this power transmission device, the frequency operation direction for decreasing the turn-on current is determined using the frequency oscillation in the optimum efficiency control. can decide.

The power control may include a power start-up process of increasing the duty of the output voltage of the inverter to a predetermined value (for example, an upper limit value) at a predetermined start-up frequency, and then manipulating the frequency so that the transmitted power reaches the target. Then, the turn-on current control may include a second process of manipulating the frequency toward the start-up frequency side when the power start-up process is being executed when the turn-on current exceeds the limit value.

If the power start-up process is in progress, the direction of frequency operation from the start-up frequency corresponds to the direction of increase in transmitted power. , the transmitted power can be reduced to lower the turn-on current.

The control unit may control the inverter to stop generation of transmission power when the turn-on current exceeds the limit value even if turn-on current control is performed.

Depending on the situation, even if turn-on current control is executed, the turn-on current may not drop below the limit value. According to this power transmission device, since power transmission is stopped in such a case, the inverter can be reliably protected.

Further, if the turn-on current exceeds the limit value even if the turn-on current control is executed, the control unit may change the start-up frequency and execute the power start-up process again after stopping the generation of the transmitted power. .

By changing the starting frequency, it may be possible to change the operating point (frequency and duty) of the inverter. For example, when the lower limit (or upper limit) of the usable frequency band is set as the starting frequency, changing the starting frequency to the upper limit (or lower limit) of the frequency band can change the operating point of the inverter. This may avoid a situation in which the turn-on current does not drop below the limit value even if turn-on current control is executed.

According to the contactless power transmission device and the contactless power transmission system according to the present disclosure, it is possible to reliably suppress the turn-on current.

1 is an overall configuration diagram of a contactless power transmission system according to an embodiment of the present disclosure; FIG. 2 is a diagram showing an example of a circuit configuration of a power transmission unit and a power reception unit shown in FIG. 1; FIG. 2 is a diagram showing a circuit configuration of an inverter shown in FIG. 1; FIG. FIG. 4 is a diagram showing switching waveforms of an inverter and waveforms of an output voltage and an output current; It is a figure which shows an example of the relationship between the power loss in a power transmission apparatus, and the frequency f of transmitted power. It is a figure which shows the operation example of the duty of an inverter output voltage, and the frequency f of transmission electric power. FIG. 4 is a diagram showing an example of frequency characteristics of turn-on current; 3 is a control block diagram of control executed by a power supply ECU; FIG. FIG. 9 is a control block diagram of an efficiency optimum control unit shown in FIG. 8; FIG. 9 is a control block diagram of a turn-on current control unit shown in FIG. 8; FIG. 11 is a control block diagram of first processing in the operation direction determination unit shown in FIG. 10; FIG. 5 is a diagram showing an example of manipulation of frequency f by turn-on current control; 4 is a flowchart showing an example of a processing procedure of turn-on current control executed by a power supply ECU; 7 is a flowchart showing an example of a processing procedure when turn-on current does not fall below a limit value even when turn-on current control is executed;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is an overall configuration diagram of a contactless power transmission system according to an embodiment of the present disclosure. Referring to FIG. 1 , this contactless power transmission system includes a power transmission device 10 and a power reception device 20 . Power receiving device 20 is mounted, for example, on a vehicle or the like that can run using power supplied from power transmitting device 10 and stored.

Power transmission device 10 includes a power factor correction (PFC) circuit 210 , an inverter 220 , a filter circuit 230 , and a power transmission section 240 . Power transmission device 10 further includes a power supply ECU (Electronic Control Unit) 250 , a communication unit 260 , a voltage sensor 270 , and current sensors 272 and 274 .

PFC circuit 210 rectifies and boosts power received from AC power supply 100 (for example, a system power supply), supplies the power to inverter 220, and improves the power factor by making the input current closer to a sine wave. Various known PFC circuits can be adopted for this PFC circuit 210 . A rectifier that does not have a power factor correction function may be used instead of the PFC circuit 210 .

Inverter 220 is controlled by power supply ECU 250 and converts DC power received from PFC circuit 210 into transmission power (AC) of a predetermined frequency (for example, several tens of kHz). By changing the switching frequency according to the drive signal from power supply ECU 250, inverter 220 can change the frequency of transmitted power in a predetermined frequency band defined by standards or the like. The transmitted power generated by inverter 220 is supplied to power transmission section 240 through filter circuit 230 . This inverter 220 is a voltage source inverter, and freewheeling diodes are connected in anti-parallel to the respective switching elements forming the inverter 220 . Inverter 220 is configured by, for example, a single-phase full bridge circuit.

Filter circuit 230 is provided between inverter 220 and power transmission section 240 and suppresses harmonic noise generated from inverter 220 . Filter circuit 230 is configured by, for example, an LC filter including inductors and capacitors.

Power transmission unit 240 receives transmission power generated by inverter 220 through filter circuit 230 and wirelessly transmits power to power reception unit 310 of power reception device 20 through a magnetic field generated around power transmission unit 240 . Power transmission unit 240 includes a resonance circuit for contactlessly transmitting power to power reception unit 310 . A resonance circuit is composed of a coil and a capacitor, but if a desired resonance state is formed only by the coil, the capacitor may not be provided.

Voltage sensor 270 detects output voltage Vo of inverter 220 and outputs the detected value to power supply ECU 250 . Current sensor 272 detects an output current Io of inverter 220 , that is, a current flowing through inverter 220 , and outputs the detected value to power supply ECU 250 . The transmitted power can be detected based on the detected values of the voltage sensor 270 and current sensor 272 . Current sensor 274 detects current Is flowing through power transmission unit 240 and outputs the detected value to power supply ECU 250 .

The power supply ECU 250 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores processing programs and the like, a RAM (Random Access Memory) that temporarily stores data, an input/output port for inputting and outputting various signals, and the like. (none of which are shown), which receives signals from the above-described sensors and the like, and executes control of various devices in the power transmission device 10 . Various controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuits). The configuration of power supply ECU 250 and the control executed by power supply ECU 250 will be described later in detail.

The communication unit 260 is configured to wirelessly communicate with the communication unit 370 of the power receiving device 20 . The communication unit 260 exchanges information regarding the start/stop of power transmission with the power receiving device 20 and receives the power receiving status of the power receiving device 20 (received voltage, received current, received power, etc.) from the power receiving device 20 .

On the other hand, power receiving device 20 includes a power receiving unit 310 , a filter circuit 320 , a rectifying unit 330 , a relay circuit 340 , and a power storage device 350 . Power receiving device 20 further includes a charging ECU 360 , a communication unit 370 , a voltage sensor 380 , and a current sensor 382 .

Power receiving unit 310 receives power (AC) output from power transmitting unit 240 of power transmitting device 10 in a contactless manner through a magnetic field. Power reception unit 310 includes a resonance circuit for contactlessly receiving power from power transmission unit 240 . A resonance circuit is composed of a coil and a capacitor, but if a desired resonance state is formed only by the coil, the capacitor may not be provided.

Filter circuit 320 is provided between power reception unit 310 and rectification unit 330 and suppresses harmonic noise generated when power reception unit 310 receives power. Filter circuit 320 is configured by, for example, an LC filter including inductors and capacitors. Rectifying unit 330 rectifies the AC power received by power receiving unit 310 and outputs the rectified AC power to power storage device 350 . Rectifying section 330 includes a rectifier and a smoothing capacitor.

Power storage device 350 is a chargeable/dischargeable power storage element. Power storage device 350 includes, for example, a secondary battery such as a lithium ion battery or a nickel-metal hydride battery, or a power storage element such as an electric double layer capacitor. Lithium-ion secondary batteries are secondary batteries that use lithium as a charge carrier, and may include so-called all-solid-state batteries that use a solid electrolyte in addition to general lithium-ion secondary batteries in which the electrolyte is a liquid. Power storage device 350 stores the power output from rectification unit 330 . Then, the power storage device 350 supplies the stored electric power to a load driving device (not shown) or the like.

Relay circuit 340 is provided between rectification unit 330 and power storage device 350 . Relay circuit 340 is turned on (conducting state) when power storage device 350 is charged by power transmission device 10 . Voltage sensor 380 detects the output voltage (power receiving voltage) of rectification unit 330 and outputs the detected value to charging ECU 360 . Current sensor 382 detects an output current (receiving current) from rectification unit 330 and outputs the detected value to charging ECU 360 . Based on the detected values of voltage sensor 380 and current sensor 382, power received by power receiving unit 310 (corresponding to charging power of power storage device 350) can be detected. Voltage sensor 380 and current sensor 382 may be provided between power receiving unit 310 and rectifying unit 330 (for example, between filter circuit 320 and rectifying unit 330).

Charging ECU 360 includes a CPU, ROM, RAM, input/output ports, etc. (none of which are shown), receives signals from the above-described sensors, etc., and controls various devices in power receiving device 20 . Various controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuits).

The communication unit 370 is configured to wirelessly communicate with the communication unit 260 of the power transmission device 10 . The communication unit 370 exchanges information regarding the start/stop of power transmission with the power transmission device 10 and transmits the power reception status of the power reception device 20 to the power transmission device 10 .

FIG. 2 is a diagram showing an example of the circuit configuration of power transmission section 240 and power reception section 310 shown in FIG. Referring to FIG. 2 , power transmission unit 240 includes a power transmission coil 242 and a capacitor 244 . Capacitor 244 is connected in series with power transmission coil 242 to form a resonance circuit with power transmission coil 242 . Capacitor 244 is provided to adjust the resonance frequency of power transmission section 240 . A Q value indicating the resonance strength of the resonance circuit formed by the power transmission coil 242 and the capacitor 244 is preferably 100 or more.

Power receiving unit 310 includes a power receiving coil 312 and a capacitor 314 . Capacitor 314 is connected in series with power receiving coil 312 to form a resonance circuit with power receiving coil 312 . Capacitor 314 is provided to adjust the resonance frequency of power reception unit 310 . It is also preferable that the Q value of the resonance circuit formed by the receiving coil 312 and the capacitor 314 is 100 or more.

In each of power transmission unit 240 and power reception unit 310, a capacitor may be connected in parallel to the coil. Further, if a desired resonance frequency can be achieved without providing a capacitor, a configuration without a capacitor may be used.

Also, the structures of the power transmitting coil 242 and the power receiving coil 312 are not particularly limited. For example, when power transmission unit 240 and power reception unit 310 face each other, power transmission coil 242 and power reception coil 312 are arranged in a spiral or helical coil wound around an axis along the direction in which power transmission unit 240 and power reception unit 310 are arranged. can be adopted for each of Alternatively, when power transmission unit 240 and power reception unit 310 face each other, a power transmission coil 242 and a power reception coil are formed by winding an electric wire around a ferrite plate whose normal direction is the direction in which power transmission unit 240 and power reception unit 310 are aligned. 312 may be employed.

Referring again to FIG. 1 , in power transmission device 10 in this contactless power transmission system, AC transmission power is supplied from inverter 220 to power transmission section 240 through filter circuit 230 . Each of power transmitting section 240 and power receiving section 310 includes a resonant circuit and is designed to resonate at the frequency of the transmitted power.

When AC transmission power is supplied from inverter 220 to power transmission unit 240 through filter circuit 230, power transmission unit 240 is supplied through a magnetic field formed between power transmission coil 242 of power transmission unit 240 and power reception coil 312 of power reception unit 310. energy (power) is transferred from to the power receiving unit 310 . The energy (power) transferred to power receiving unit 310 is supplied to power storage device 350 through filter circuit 320 and rectifying unit 330 .

FIG. 3 shows a circuit configuration of inverter 220 shown in FIG. Referring to FIG. 3, inverter 220 is a voltage type inverter and includes power semiconductor switching elements (hereinafter also simply referred to as "switching elements") Q1-Q4 and freewheeling diodes D1-D4. A PFC circuit 210 (FIG. 1) is connected to terminals T1 and T2 on the DC side, and a filter circuit 230 (FIG. 1) is connected to terminals T3 and T4 on the AC side.

The switching elements Q1 to Q4 are composed of, for example, IGBTs (Insulated Gate Bipolar Transistors), bipolar transistors, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), GTOs (Gate Turn Off thyristors), and the like. Freewheeling diodes D1-D4 are connected in antiparallel to switching elements Q1-Q4, respectively.

A DC voltage V1 output from the PFC circuit 210 is applied between the terminals T1 and T2. Along with the switching operations of the switching elements Q1 to Q4, an output voltage Vo and an output current Io are generated between the terminals T3 and T4 (in the drawing, the direction indicated by the arrow is a positive value). As an example, FIG. 3 shows a state in which the switching elements Q1 and Q4 are ON, the switching elements Q2 and Q3 are OFF, and the output voltage Vo is the voltage V1 (positive value).

FIG. 4 is a diagram showing switching waveforms of inverter 220 and waveforms of output voltage Vo and output current Io. In the figure, T indicates the switching period of inverter 220 . That is, the switching frequency of inverter 220 is 1/T.

Referring to FIG. 3 together with FIG. 4, by turning ON/OFF the switching elements Q1 to Q4 as shown, a square-wave output voltage Vo that fluctuates at the switching frequency is generated. That is, by manipulating (changing) the switching frequency of inverter 220, the frequency of the transmitted power generated by inverter 220 can be adjusted.

Td indicates the output time of the output voltage Vo. The period ratio of Td to period T is defined as the duty of the inverter output voltage. By changing the on/off timing (on/off period ratio 0.5) of the switching elements Q2 and Q4 with respect to the on/off timing (on/off period ratio 0.5) of the switching elements Q1 and Q3, the inverter The duty of the output voltage can be adjusted. FIG. 4 shows a case where the duty is 0.25, and the upper limit of the duty is 0.5.

By adjusting the duty of this output voltage Vo, transmitted power can be changed. Qualitatively, the transmitted power can be increased by increasing the duty, and the transmitted power can be decreased by decreasing the duty. In this embodiment, power supply ECU 250 performs transmission power control for controlling transmission power to target power by manipulating the duty of output voltage Vo.

The instantaneous value of the output current Io at the rising edge of the output voltage Vo (time t4 or time t8) indicates the turn-on current It. The value of the turn-on current It varies depending on the voltage V1 applied from the PFC circuit 210 to the inverter 220 and the switching frequency of the inverter 220 (the frequency of transmitted power).

FIG. 4 shows an example in which a positive turn-on current It flows. When the positive turn-on current It flows, a reverse short-circuit current (recovery current) flows through the freewheeling diode D3 connected in antiparallel to the switching element Q3 when the output voltage Vo rises (time t4 or time t8). As a result, the freewheeling diode D3 through which the short-circuit current flows and the switching element Q1 generate more heat, and the loss of the inverter 220 increases.

Main power losses in the power transmission device 10 are switching losses and conduction losses. A switching loss is a power loss that occurs when the inverter 220 is switched (turned on or turned off). In the power transmission device 10, the power loss due to the turn-on current It during the switching operation of the inverter 220 is the dominant switching loss. On the other hand, conduction loss is power loss caused by conduction. In the power transmission device 10 , power loss due to heat generation or the like accompanying the conduction of the power transmission coil 242 and the inverter 220 is the dominant conduction loss.

In this embodiment, power supply ECU 250 detects power loss in power transmission device 10 . Specifically, the sum of the power loss due to turn-on current It, the power loss due to the current flowing through power transmission coil 242 , and the power loss due to the current flowing through inverter 220 is detected as the power loss in power transmission device 10 .

Power loss in the power transmission device 10 varies depending on the switching frequency of the inverter 220 (the frequency of transmitted power). FIG. 5 is a diagram showing an example of the relationship between the power loss in the power transmission device 10 and the frequency f of the transmitted power. In FIG. 5, fa and fb respectively denote the lower and upper limits of the usable frequency band defined by the standard or the like.

Referring to FIG. 5, the relationship between frequency f (horizontal axis) of transmitted power and power loss (vertical axis) in power transmission device 10 is indicated by a downwardly convex curve k. When the frequency f is the optimum frequency fx, the power loss in the power transmission device 10 is minimized (local minimum value Lx).

Therefore, in this embodiment, power supply ECU 250 manipulates frequency f of transmitted power (manipulates the switching frequency of inverter 220) to minimize power loss in power transmission device 10 and improve efficiency. Execute control. Although the details will be described later, power supply ECU 250 searches for optimum frequency fx by oscillating frequency f (extremum search), and executes control to converge frequency f to optimum frequency fx.

In this embodiment, the optimum efficiency control minimizes the sum of the power loss due to the turn-on current It, the power loss due to the current flowing through the power transmission coil 242, and the power loss due to the current flowing through the inverter 220. However, efficiency optimum control may be performed to minimize either of these power losses or the sum of the two.

When the turn-on current It increases, the recovery current (short-circuit current) also increases, and there is a possibility that the freewheeling diode and the switching element through which the short-circuit current flows may overheat. Therefore, in this embodiment, a limit value is set for turn-on current It, and power supply ECU 250 executes turn-on current control to control turn-on current It to be equal to or less than the limit value. Since the value of turn-on current It varies depending on the switching frequency of inverter 220, power supply ECU 250 manipulates frequency f of transmitted power (manipulates the switching frequency of inverter 220) when turn-on current It exceeds the limit value. Lower turn-on current.

Note that both the turn-on current control and the above-described efficiency optimum control manipulate the frequency f, and both controls may interfere with each other. Turn-on current control is performed from the viewpoint of protecting inverter 220, and has a higher priority than efficiency optimum control. Therefore, in this embodiment, turn-on current control is executed with priority over efficiency optimum control. That is, when turn-on current It exceeds the limit value, power supply ECU 250 stops the optimum efficiency control and executes the turn-on current control if the optimum efficiency control is being executed. Then, when the turn-on current It becomes equal to or less than the limit value, the turn-on current control is deactivated, so the efficiency optimum control is resumed.

FIG. 6 is a diagram showing an operation example of the duty of the inverter output voltage and the frequency f of the transmitted power. FIG. 6 shows an operation example of duty and frequency f immediately after the start of power transmission.

Referring to FIG. 6, each of lines PL1 and PL2 indicates contour lines of transmitted power. The transmitted power indicated by line PL1 is greater than the transmitted power indicated by line PL2. As can be seen from the figure, the duty for realizing a certain transmission power shows frequency dependence. In this example, it is assumed that the transmission power indicated by line PL1 is the target power.

When the start of power transmission is instructed by a user's operation or the arrival of time by a timer, etc., power supply ECU 250 executes a power start-up process to raise the transmitted power to reach the target power. Specifically, power supply ECU 250 first sets the operating frequency (frequency f of transmitted power) of inverter 220 to a predetermined startup frequency, starts power transmission, and increases the duty (line A in the figure). In this example, the upper limit fb of the usable frequency band defined by standards or the like is set as the startup frequency. Note that the activation frequency is not limited to this, and may be a frequency different from the lower limit fa, the lower limit fa, and the upper limit fb of the frequency band.

In this example, in a frequency range intermediate between the lower limit fa and the upper limit fb (hereinafter referred to as "intermediate range"), transmitted power can be obtained with a lower duty than frequencies close to the lower limit fa and the upper limit fb. Therefore, in the intermediate range, the turn-on current It tends to increase due to the high power factor, and there is a high possibility that the turn-on current It will exceed the limit value. Therefore, in this example, the upper limit fb (or the lower limit fa) of the frequency band is set as the activation frequency, and the frequency f is adjusted from the activation frequency.

When the duty reaches the upper limit (0.5), power supply ECU 250 manipulates frequency f while maintaining the duty at the upper limit (line B in the figure). In this example, since the upper limit fb of the frequency band is set as the startup frequency, power supply ECU 250 reduces the frequency f to bring the transmitted power closer to the target power.

Then, when the transmitted power reaches the target power (line PL1), power supply ECU 250 ends the power startup process, maintains the transmitted power at the target power by adjusting the duty, and operates frequency f by efficiency optimum control. (line C in the figure). As a result, it is possible to realize highly efficient power transmission while controlling the power to be transmitted to the target power.

Note that the above power activation process also manipulates the frequency f, and the turn-on current control and the power activation process interfere with each other (the optimum efficiency control operates after the power activation process is executed, so the optimum efficiency control and the power does not interfere with the startup process). Therefore, in this embodiment, turn-on current control is executed with priority over the above-described power activation process. That is, when the turn-on current It exceeds the limit value and the frequency f is being operated by the power start-up process (line B in the figure), the power supply ECU 250 stops the power start-up process and executes turn-on current control. .

FIG. 7 is a diagram showing an example of frequency characteristics of the turn-on current It. Referring to FIG. 7, dotted line L1 shows an example of the frequency characteristic of turn-on current It immediately after the start of power transmission. A solid line L2 shows an example of the frequency characteristic of the turn-on current It after a certain amount of time has passed since the start of power transmission. In this way, the frequency characteristic of the turn-on current It may change during power transmission. For example, if the coupling coefficient between the coils, the temperature, or the like changes during power transmission, the frequency characteristic of the turn-on current It may change.

When the turn-on current It reaches the limit value It_lim when the frequency f is changed from the startup frequency side (reduced from the upper limit fb in this example), the frequency f is operated to the original startup frequency side (increased in this example). It is also considered that the turn-on current It can be reduced by doing so.

However, when the turn-on current It reaches the limit value It_lim during execution of the optimum efficiency control, if the frequency characteristic of the turn-on current It changes as shown by the solid line L2, the frequency f is shifted to the original starting frequency side. When operated (increased in this example), the turn-on current It rather increases. Therefore, when the turn-on current It reaches the limit value It_lim, the turn-on current It cannot be reliably reduced by control that uniformly changes the frequency f toward the startup frequency.

Therefore, in the contactless power transmission system according to this embodiment, power supply ECU 250 changes frequency f of transmitted power and detects a change in turn-on current It at that time. Then, power supply ECU 250 determines the operating direction of frequency f to decrease turn-on current It based on the direction of change in turn-on current It according to change in frequency f. As a result, the turn-on current It can be reliably suppressed.

In this embodiment, in the optimum efficiency control, the optimum frequency fx is searched for by oscillating the frequency f. Therefore, in this non-contact power transmission system, the direction of change in the turn-on current It corresponding to the change in the frequency f is detected using the oscillation of the frequency f by the efficiency optimum control, and based on the detection result, the turn-on current A manipulation direction of the frequency f that lowers It is determined. As a result, it is possible to determine the operating direction of the frequency that reduces the turn-on current It while cooperating with the efficiency optimum control.

If the frequency f is being operated by the power activation process (line B in FIG. 6), the transmitted power is reduced by returning the frequency f to the activation frequency side, and the turn-on current It is accordingly decreased. Therefore, in this non-contact power transmission system, when turn-on current It exceeds the limit value, power supply ECU 250 changes the direction of change in turn-on current It according to the change in frequency f if the power startup process is being executed. The frequency f is operated to the activation frequency side without detecting .

FIG. 8 is a control block diagram of control executed by power supply ECU 250. As shown in FIG. 8, power supply ECU 250 includes power transmission control unit 410, efficiency optimum control unit 420, turn-on current control unit 430, turn-on current detection unit (hereinafter also referred to as "It detection unit") 440, A frequency setting section 450 and a drive signal generation section 460 are included.

Transmitted power control unit 410 receives target power Psr indicating a target of transmitted power Ps and a detected value of transmitted power Ps. Target power Psr is generated, for example, based on the power reception status of power receiving device 20 . In this embodiment, the power receiving device 20 generates the target power Psr based on the deviation between the target of the received power and the detected value, and transmits the target power Psr from the power receiving device 20 to the power transmitting device 10 . Transmitted power Ps is calculated, for example, based on the detected values of voltage sensor 270 and current sensor 272 (FIG. 1).

When instructed to start power transmission, power transmission control unit 410 executes a power start-up process for raising transmitted power Ps and causing transmitted power Ps to reach target power Psr. This power start-up process is a feedforward (FF) control that operates the duty and the frequency f according to a predetermined procedure, unlike the feedback (FB) that controls the duty based on the power deviation, which will be described later.

Specifically, transmitted power control unit 410 sets the operating frequency of inverter 220 (frequency f of transmitted power) to a predetermined startup frequency, and sets the duty command value duty, which is the command value of the duty of the inverter output voltage, to the upper limit ( 0.5). The duty command value duty is output to drive signal generator 460 .

Then, when the duty reaches the upper limit, transmitted power control unit 410 outputs frequency manipulation amount Δf1 in the direction in which transmitted power Ps increases while maintaining duty command value duty at the upper limit. Frequency manipulated variable Δf 1 is output to frequency setting unit 450 . This frequency manipulated variable Δf1 is predetermined according to the starting frequency. A frequency manipulated variable Δf1 of value is output. This frequency manipulation amount Δf1 is output until the transmitted power Ps reaches the target power Psr.

When the transmitted power Ps reaches the target power Psr by the above-described power activation process, the transmitted power control unit 410 ends the power activation process and sets the power FB based on the deviation (power deviation) between the target power Psr and the transmitted power Ps. Execute control. For example, transmission power control unit 410 calculates an operation amount by executing PI control or the like using the power deviation as an input, and outputs the calculated operation amount to drive signal generation unit 460 as a duty command value duty.

Transmission power control unit 410 outputs a notification to that effect to efficiency optimum control unit 420 and turn-on current control unit 430 during execution of power activation processing. This is because the optimum efficiency control is deactivated in the optimum efficiency control unit 420 during execution of the power activation process. This is because, in the turn-on current control unit 430, the process of determining the operation direction of the frequency f differs during execution of the power startup process and during execution of the efficiency optimum control following the power startup process, as described above.

On the other hand, when transmission power control section 410 receives notification from turn-on current control section 430 that turn-on current control is in operation, transmission power control section 410 stops transmission power control. Specifically, power transmission control unit 410 maintains duty command value duty at the previous value, and outputs frequency operation amount Δf1 as 0 when a non-zero frequency operation amount Δf1 is being output.

It detector 440 detects turn-on current It based on the detected values of output voltage Vo and output current Io of inverter 220 . Specifically, It detection unit 440 detects the rise of output voltage Vo, and detects the detected value of output current Io at the rise of output voltage Vo as turn-on current It.

Efficiency optimum control unit 420 receives the value of turn-on current It detected by It detection unit 440 , the value of current Is flowing through power transmitting coil 242 , and the value of output current Io of inverter 220 . Efficiency optimum control section 420 detects power loss in power transmission device 10 based on each of these detected values, and searches for optimum frequency fx at which the power loss is minimized (minimum). That is, optimum efficiency control section 420 calculates frequency manipulation amount Δf2 in the direction in which frequency f approaches optimum frequency fx, and outputs it to frequency setting section 450 .

Efficiency optimum control unit 420 also stops the efficiency optimum control when it receives notification from turn-on current control unit 430 that turn-on current control is in operation. That is, efficiency optimum control unit 420 outputs 0 as frequency manipulated variable Δf2.

Furthermore, even when receiving a notification from transmission power control unit 410 indicating that the power activation process is being executed, optimum efficiency control unit 420 deactivates the optimum efficiency control. That is, efficiency optimum control unit 420 outputs 0 as frequency manipulated variable Δf2.

FIG. 9 is a control block diagram of efficiency optimum control section 420 shown in FIG. 9, efficiency optimum control unit 420 includes vibration signal generation unit 421, loss detection unit 422, high pass filter (HPF (High Pass Filter)) 423, multiplication unit 424, and low pass filter (LPF ( Low Pass Filter)) 425 , a controller 426 and an adder 427 .

The vibration signal generator 421 generates a vibration signal Sv for vibrating the frequency f and outputs it to the multiplier 424 and the adder 427 . The vibration signal Sv is a pulse signal having a predetermined amplitude that is repeatedly turned on/off at a predetermined vibration cycle. In the extremum search adopted in the optimum efficiency control executed by the optimum efficiency control unit 420, the vibration signal Sv is used to find the optimum frequency fx of the frequency f (the power loss in the power transmission device 10 is minimized (minimum) frequency) is monitored.

The loss detection unit 422 detects power loss in the power transmission device 10 based on each detected value of the turn-on current It, the current Is flowing through the power transmission coil 242 , and the output current Io of the inverter 220 . The detected power loss is the sum of the power loss due to the turn-on current, the power loss due to the current flowing through power transmission coil 242 , and the power loss due to the current flowing through inverter 220 . The detected value of output current Io corresponds to the current flowing through inverter 220 .

Information indicating the relationship between the turn-on current It, the current Is, and the current Io and the power loss (hereinafter referred to as "loss information") is used to detect the power loss. The loss detection unit 422 can obtain the power loss from the detected values of the turn-on current It, the current Is, and the current Io by referring to the loss information stored in advance in the ROM of the power supply ECU 250 . Loss information can be maps, formulas, or models.

The loss detection unit 422 repeatedly detects power loss at a predetermined cycle. A power loss waveform Lv1 is generated by periodically detecting the power loss. The loss detection unit 422 outputs the generated power loss waveform Lv1 to the HPF 423 .

The HPF 423 extracts the high-frequency component Lv2 from the power loss waveform Lv1 (a signal obtained by removing the DC component from the power loss waveform Lv1) and outputs the extracted signal to the multiplier 424 . This high frequency component Lv2 indicates the amount of change in power loss when the frequency f is vibrated by the vibration signal Sv.

The multiplier 424 multiplies the vibration signal Sv by the high frequency component Lv2 to calculate the correlation coefficient between the vibration signal Sv and the high frequency component Lv2. This correlation coefficient indicates the direction of increase or decrease in power loss with respect to changes in frequency f.

LPF 425 extracts the DC component of the correlation coefficient calculated by multiplier 424 . The output of this LPF 425 indicates the operation direction (increase/decrease direction) of the frequency f for shifting the frequency f to the optimum frequency fx. Note that the LPF 425 may be omitted if the output noise of the multiplier 424 is small.

Based on the output of the LPF 425, the controller 426 calculates the amount of operation (change amount) of the frequency f for shifting the frequency f to the optimum frequency fx. The controller 426 calculates the manipulated variable of the frequency f by, for example, executing I control (integral control) with the output signal of the LPF 425 as input.

The adder 427 adds the vibration signal Sv generated by the vibration signal generator 421 to the output of the controller 426, and outputs the calculated value to the frequency setting unit 450 (FIG. 8) as the final frequency manipulated variable Δf2. . Through the control described above, the optimum frequency fx that minimizes the power loss in power transmission device 10 is searched for, and the power loss in power transmission device 10 can be minimized.

Referring to FIG. 8 again, turn-on current control unit 430 receives the value of turn-on current It detected by It detection unit 440 . Then, when turn-on current It exceeds the limit value, turn-on current control unit 430 calculates a frequency manipulation amount Δf3 in the direction of decreasing turn-on current It and outputs it to frequency setting unit 450 . When the turn-on current It is equal to or less than the limit value (when the turn-on current control is not activated), the turn-on current control unit 430 outputs 0 as the frequency manipulated variable Δf3.

Turn-on current control unit 430 receives notification from transmission power control unit 410 that power activation processing is being executed. This notification is used to determine whether power transmission control section 410 is executing power activation processing, or whether efficiency optimum control is being executed by efficiency optimization control section 420 subsequent to the power activation processing. . Note that turn-on current control unit 430 may receive notification from optimum efficiency control unit 420 indicating that optimum efficiency control is being executed in order to determine whether optimum efficiency control is being executed.

In addition, turn-on current control unit 430 outputs a notification to that effect to power transmission control unit 410 and optimum efficiency control unit 420 during execution of turn-on current control (while turn-on current It exceeds the limit value). As described above, according to this notification, transmission power control (including power startup processing) in transmission power control section 410 and efficiency optimum control in efficiency optimum control section 420 are stopped during execution of turn-on current control.

FIG. 10 is a control block diagram of turn-on current controller 430 shown in FIG. Referring to FIG. 10 , turn-on current control portion 430 includes an execution determination portion 431 , an operation direction determination portion 432 and an operation amount calculation portion 437 .

Execution determination unit 431 determines whether or not turn-on current It exceeds a limit value. This limit value is a positive value and is appropriately set based on the resistance of inverter 220 to recovery current. Then, when turn-on current It exceeds the limit value, execution determination unit 431 outputs a signal instructing execution of turn-on current control to operation direction determination unit 432 . Based on this signal, a notification indicating that turn-on current control is being executed is output to transmission power control section 410 and efficiency optimum control section 420 .

The operation direction determination unit 432 determines the operation direction Dr of the frequency at which the turn-on current It decreases during execution of turn-on current control. The method of determining the operation direction Dr of the frequency f differs between when efficiency optimum control is being performed by efficiency optimum control section 420 and when power transmission power control section 410 is performing power activation processing.

If the execution determination unit 431 determines that the turn-on current It exceeds the limit value, and the optimum efficiency control is being executed, the operation direction determination unit 432 determines the turn-on current It when the frequency f is changed. The operation direction Dr is determined based on the direction of change in (first processing). In this embodiment, as means for changing the frequency f in the first processing, the vibration signal Sv in the optimum efficiency control is used as described above. On the other hand, if it is determined that the turn-on current It exceeds the limit value and the power activation process is being executed, the operation direction determination unit 432 controls the operation direction Dr so as to operate the frequency f toward the activation frequency side. is determined (second processing).

FIG. 11 is a control block diagram of the first process in the operation direction determining section 432 shown in FIG. Referring to FIG. 11 , operation direction determining portion 432 includes an HPF 433 , a multiplying portion 434 , an LPF 435 and a sign extracting portion 436 .

HPF 433 extracts high frequency component Lv3 from the waveform of turn-on current It and outputs it to multiplier 434 . This high frequency component Lv3 indicates the amount of change in the turn-on current It when the frequency f is vibrated by the vibration signal Sv.

The multiplier 434 calculates the correlation coefficient between the vibration signal Sv and the high frequency component Lv3 by multiplying the high frequency component Lv3 output from the HPF 433 by the vibration signal Sv. This correlation coefficient indicates the direction in which the turn-on current It increases or decreases with respect to the frequency f.

LPF 435 extracts the DC component of the correlation coefficient calculated by multiplier 434 . The sign extracting unit 436 inverts the sign of the output of the LPF 435 and outputs it. The code obtained by this code extractor 436 indicates the operating direction Dr of the frequency for decreasing the turn-on current It.

Referring to FIG. 10 again, operation amount calculation unit 437 calculates frequency operation amount Δf3 in the direction of decreasing turn-on current It based on operation direction Dr of frequency f determined by operation direction determination unit 432 . For example, the operation amount calculator 437 calculates a value obtained by multiplying a preset frequency change amount (positive value) by the operation direction Dr as the frequency operation amount Δf3.

FIG. 12 is a diagram showing an example of manipulation of the frequency f by turn-on current control. Referring to FIG. 12, when turn-on current It exceeds limit value It_lim at time t1, turn-on current control unit 430 determines the operating direction of the frequency for decreasing turn-on current It. In this example, it is determined that the operating direction of the frequency that lowers the turn-on current It is the direction that lowers the frequency f. Then, the turn-on current control reduces the frequency f by the frequency manipulation amount Δf3, and as a result, the turn-on current It is reduced to the limit value It_lim or less.

When turn-on current It again exceeds limit value It_lim at time t2 due to changes in the coupling coefficient, temperature, etc., turn-on current control unit 430 again determines the operating direction of the frequency for decreasing turn-on current It. Here, too, the direction of operation of the frequency f is determined to be the direction of decreasing the frequency f, and the turn-on current control decreases the frequency f by the frequency operation amount Δf3, and as a result, the turn-on current It decreases to the limit value It_lim or less. is doing.

Referring to FIG. 8 again, frequency setting unit 450 adds the integrated value of frequency manipulated variable Δf1, the integrated value of frequency manipulated variable Δf2, and the integrated value of frequency manipulated variable Δf3 to the activation frequency, and sets the calculation result to the frequency. It is output to the drive signal generator 460 as the command value of f.

Drive signal generation unit 460 generates a drive signal for inverter 220 based on the duty command value duty received from power transmission control unit 410 and the command value for frequency f received from frequency setting unit 450 . By driving the inverter 220 according to the drive signal generated by the drive signal generation unit 460, the duty of the output voltage Vo of the inverter 220 becomes a value corresponding to the duty command value duty, and the frequency f of the transmitted power becomes the command value. is a value corresponding to

FIG. 13 is a flow chart showing an example of a procedure of turn-on current control executed by power supply ECU 250. Referring to FIG. A series of processes shown in this flowchart are repeatedly executed at predetermined time intervals.

Referring to FIG. 13, power supply ECU 250 detects turn-on current It and determines whether the detected turn-on current It exceeds limit value It_lim (step S10). If turn-on current It is equal to or less than limit value It_lim (NO in step S10), power supply ECU 250 shifts the process to RETURN without executing the subsequent series of processes.

When it is determined in step S10 that turn-on current It exceeds limit value It_lim (YES in step S10), power supply ECU 250 determines whether power activation processing is being performed (step S20).

When it is determined in step S20 that power activation processing is being performed (YES in step S20), power supply ECU 250 stops the power activation processing and operates frequency f toward the activation frequency side (step S30). Specifically, power supply ECU 250 maintains the duty of output voltage Vo of inverter 220 at the previous value (upper limit), sets frequency manipulated variable Δf1 by power start-up processing to 0, and sets the starting frequency according to frequency manipulated variable Δf3 by turn-on current control. The inverter 220 is controlled to change the frequency f to the side.

On the other hand, if it is determined in step S20 that the power activation process is not being performed, that is, that the optimum efficiency control is being executed (NO in step S20), power supply ECU 250 causes vibration of frequency f by vibration signal Sv in the optimum efficiency control. is used to detect the direction of change in the turn-on current It corresponding to the change in the frequency f, and the operating direction Dr of the frequency for decreasing the turn-on current It is determined (step S40).

Then, power supply ECU 250 stops the optimum efficiency control and operates frequency f in operation direction Dr determined in step S40 (step S50). Specifically, power supply ECU 250 controls inverter 220 so that frequency manipulation amount Δf2 by efficiency optimum control is 0, and frequency f is changed in the above-described manipulation direction Dr according to frequency manipulation amount Δf3 by turn-on current control.

As described above, according to this embodiment, when the turn-on current It exceeds the limit value It_lim, the turn-on current It is determined (during execution of optimum efficiency control), the turn-on current It can be reliably suppressed.

When the turn-on current It exceeds the limit value It_lim, if the power activation process is in progress, the frequency f is activated because the direction of operation of the frequency f from the activation frequency corresponds to the direction of increase in the transmitted power. By manipulating to the frequency side, it is possible to lower the transmitted power and lower the turn-on current It.

Further, according to this embodiment, since the operation direction Dr of the frequency for decreasing the turn-on current It is determined by utilizing the vibration of the frequency f caused by the vibration signal Sv in the optimum efficiency control, the frequency f can be determined in cooperation with efficiency optimum control.

Depending on the situation, turn-on current It may not drop below the limit value even if turn-on current control is executed. That is, the turn-on current control is a control for manipulating the frequency f so as to reduce the turn-on current It when the turn-on current It exceeds the limit value. However, depending on the situation, the turn-on current It may not drop below the limit value.

In such a case, it is preferable to temporarily stop power transmission in order to protect inverter 220 . Further, power transmission is restarted after power transmission is temporarily stopped, and if the turn-on current It does not fall below the limit value even after such power transmission is stopped and restarted repeatedly, the startup frequency is changed and power transmission is restarted. preferable. By changing the startup frequency, the operating point (frequency and duty) of the inverter 220 is changed, and it is possible to avoid the situation where the turn-on current It does not drop below the limit value even if the turn-on current control is executed.

FIG. 14 is a flowchart showing an example of a processing procedure when turn-on current It does not fall below a limit value even when turn-on current control is executed. A series of processes shown in this flowchart are also repeatedly executed at predetermined time intervals.

Referring to FIG. 14, power supply ECU 250 determines whether or not the state in which turn-on current It exceeds limit value It_lim (the state in which YES is determined in step S10 of FIG. 13) has continued for a predetermined time. (Step S110). The predetermined time is set, for example, based on the expected maximum time (design value) until the turn-on current It falls below the limit value due to execution of turn-on current control. If the above state has not continued for a predetermined period of time (NO in step S110), power supply ECU 250 shifts the process to RETURN without executing the subsequent series of processes.

When it is determined in step S110 that the state in which turn-on current It exceeds limit value It_lim has continued for a predetermined time (YES in step S110), power supply ECU 250 causes inverter 220 to stop generating transmitted power. to temporarily stop power transmission (step S120). Turn-on current control is also stopped by stopping power transmission.

Thereafter, power supply ECU 250 determines whether or not the number of re-executions of the power start-up process has reached a specified number of times before re-executing the power start-up process (step S130). An appropriate number of times, such as two times or more, is set as the specified number of times.

When it is determined in step S130 that the number of re-executions has not reached the prescribed number (NO in step S130), power supply ECU 250 re-executes the power startup process from the startup frequency of the previous power startup process (step S140). . It should be noted that a certain period of time may be provided from when power transmission is temporarily stopped to when the power activation process is re-executed.

On the other hand, when it is determined in step S130 that the number of times of re-execution has reached the specified number of times (YES in step S130), power supply ECU 250 changes the activation frequency and executes the power activation process again (step S150). For example, in the previous power startup process, if the upper limit fb of the usable frequency band defined by the standard or the like was used as the startup frequency, the startup frequency is changed to the lower limit fa of the frequency band, and the power startup process is executed again. be done. This may avoid a situation where the turn-on current It does not decrease even if the turn-on current control is executed when the operating point of the inverter 220 changes and the turn-on current It reaches the limit value.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

10 Power Transmission Device 20 Power Reception Device 100 AC Power Supply 210 PFC Circuit 220 Inverter 230,320 Filter Circuit 240 Power Transmission Unit 242 Power Transmission Coil 244,314 Capacitor 250 Power Supply ECU 260,370 Communication Unit 270, 380 voltage sensor, 272, 274, 382 current sensor, 310 power receiving unit, 312 power receiving coil, 330 rectifying unit, 340 relay circuit, 350 power storage device, 360 charging ECU, 410 transmission power control unit, 420 optimum efficiency control unit, 421 vibration Signal generation unit 422 Loss detection unit 423, 433 HPF 424, 434 Multiplication unit 425, 435 LPF 426 Controller 427 Addition unit 430 Turn-on current control unit 431 Execution determination unit 432 Operation direction determination unit 436 Code extractor 437 Manipulated variable calculator 440 It detector 450 Frequency setter 460 Drive signal generator.

Claims (5)

a power transmission unit configured to wirelessly transmit power to a power receiving device;
an inverter that generates transmission power of a predetermined frequency and supplies it to the power transmission unit;
and a control unit,
The control unit
power control for controlling the transmitted power with a target;
Efficiency optimum control for searching for an optimum frequency for improving efficiency by oscillating the frequency while the transmitted power is controlled to a target by the power control ;
a turn-on current control for controlling the turn-on current to a limit value or less by manipulating the frequency by the inverter ,
The turn-on current control includes a first process of determining a direction of frequency operation for decreasing the turn-on current based on a direction of change in the turn-on current when the frequency is changed,
The contactless power transmission device, wherein the first process includes a process of determining an operation direction of the frequency based on a direction of change of the turn-on current according to oscillation of the frequency in the optimum efficiency control. The power control includes power activation processing in which the duty of the output voltage of the inverter is increased to a predetermined value at a predetermined activation frequency, and then the transmitted power reaches a target by manipulating the frequency,
2. The turn-on current control further includes a second process of manipulating the frequency toward the start-up frequency when the power start-up process is being executed when the turn-on current exceeds the limit value. The contactless power transmission device according to . a power transmission unit configured to wirelessly transmit power to a power receiving device;
an inverter that generates transmission power of a predetermined frequency and supplies it to the power transmission unit;
a control unit configured to execute turn-on current control for controlling a turn-on current to a limit value or less by manipulating the frequency by the inverter;
The turn-on current control includes processing for determining a direction of operation of the frequency for decreasing the turn-on current based on the direction of change in the turn-on current when the frequency is changed,
The contactless power transmission device , wherein the control unit controls the inverter to stop generating the transmission power when the turn-on current exceeds the limit value even if the turn-on current control is executed. a power transmission unit configured to wirelessly transmit power to a power receiving device;
an inverter that generates transmission power of a predetermined frequency and supplies it to the power transmission unit;
and a control unit,
The control unit
power control for controlling the transmitted power with a target;
a turn-on current control for controlling the turn-on current to a limit value or less by manipulating the frequency by the inverter,
The turn-on current control includes a first process of determining a direction of frequency operation for decreasing the turn-on current based on a direction of change in the turn-on current when the frequency is changed,
The power control includes power activation processing in which the duty of the output voltage of the inverter is increased to a predetermined value at a predetermined activation frequency, and then the transmitted power reaches a target by manipulating the frequency,
The turn-on current control further includes a second process of manipulating the frequency toward the start-up frequency when the power start-up process is being executed when the turn-on current exceeds the limit value,
The control unit
controlling the inverter to stop generating the transmission power when the turn-on current exceeds the limit value even if the turn-on current control is executed;
A contactless power transmission device that, after stopping generation of the transmitted power, changes the activation frequency and executes the power activation process again. a power transmission device;
a power receiving device that receives power from the power transmitting device in a contactless manner;
The power transmission device
a power transmission unit configured to wirelessly transmit power to the power receiving device;
an inverter that generates transmission power of a predetermined frequency and supplies it to the power transmission unit;
a control unit;
The control unit
power control for controlling the transmitted power with a target;
Efficiency optimum control for searching for an optimum frequency for improving efficiency by oscillating the frequency while the transmitted power is controlled to a target by the power control;
a turn-on current control for controlling the turn-on current to a limit value or less by manipulating the frequency by the inverter,
The turn-on current control includes processing for determining a direction of operation of the frequency for decreasing the turn-on current based on the direction of change in the turn-on current when the frequency is changed,
The non-contact power transmission system , wherein the processing includes processing for determining the operating direction of the frequency based on the direction of change in the turn-on current according to the oscillation of the frequency in the efficiency optimum control .

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